ISTANBUL (Reuters) - Turkish police detained 75 suspected Islamic State members in two operations on Friday, state media and police said, after arresting about 120 such suspects across Turkey a day earlier, tightening security ahead of the New Year.

Some 500 police officers took part in simultaneous raids across Ankara, and many of those detained were foreign nationals, state-run Anadolu news agency reported.

It said prosecutors in the Turkish capital issued arrest warrants for 46 people and had so far detained 29 of them. Materials seized in the raids indicated some of the suspects had made preparations for an attack over New Year, it added.

Separately, police raided 25 different addresses in Istanbul on Friday and detained 46 suspected members of Islamic State, 43 of whom were foreigners, a police statement said. The suspects were involved in smuggling and theft for the group, it said.

During New Year's celebrations a year ago, a man with an assault rifle shot dead 39 people including Turks and visitors from several Arab nations, India and Canada at an exclusive nightclub in Turkey's largest city Istanbul.

Islamic State claimed responsibility for that shooting, one of a series of attacks believed to have been carried out by the jihadists and Kurdish militants in Turkey in the last couple of years. A trial of those allegedly involved in the nightclub attack began this month.

On New Year's Eve, Turkey will more than double the number of police officers on duty in Istanbul to 37,000 and cancel or ban public celebrations in key districts of the city for security reasons, officials have said.

For the same reason, access to Ankara's central Kizilay square will not be allowed on Dec. 31, media reports said.

Among other security measures, many roads in central Istanbul districts will be closed on New Year's Eve, while heavy vehicles will not be allowed to enter seven districts, another police statement said.

(Writing by Daren Butler and Ali Kucukgocmen; Editing by Kim Coghill, William Maclean)